Nanovaccines: An effective therapeutic approach for cancer therapy

Cancer vaccines hold considerable promise for the immunotherapy of solid tumors. Nanomedicine offers several strategies for enhancing vaccine effectiveness. In particular, molecular or (sub) cellular vaccines can be delivered to the target lymphoid tissues and cells by nanocarriers and nanoplatforms to increase the potency and durability of antitumor immunity and minimize negative side effects. Nanovaccines use nanoparticles (NPs) as carriers and/or adjuvants, offering the advantages of optimal nanoscale size, high stability, ample antigen loading, high immunogenicity, tunable antigen presentation, increased retention in lymph nodes, and immunity promotion. To induce antitumor immunity, cancer vaccines rely on tumor antigens, which are administered in the form of entire cells, peptides, nucleic acids, extracellular vesicles (EVs), or cell membrane-encapsulated NPs. Ideal cancer vaccines stimulate both humoral and cellular immunity while overcoming tumor-induced immune suppression. Herein, we review the key properties of nanovaccines for cancer immunotherapy and highlight the recent advances in their development based on the structure and composition of various (including synthetic and semi (biogenic) nanocarriers. Moreover, we discuss tumor cell-derived vaccines (including those based on whole-tumor-cell components, EVs, cell membrane-encapsulated NPs, and hybrid membrane-coated NPs), nanovaccine action mechanisms, and the challenges of immunocancer therapy and their translation to clinical applications.

Methods for Engineering Binders to Multi-Pass Membrane Proteins

Numerous potential drug targets, including G-protein-coupled receptors and ion channel proteins, reside on the cell surface as multi-pass membrane proteins. Unfortunately, despite advances in engineering technologies, engineering biologics against multi-pass membrane proteins remains a formidable task. In this review, we focus on the different methods used to prepare/present multi-pass transmembrane proteins for engineering target-specific biologics such as antibodies, nanobodies and synthetic scaffold proteins. The engineered biologics exhibit high specificity and affinity, and have broad applications as therapeutics, probes for cell staining and chaperones for promoting protein crystallization. We primarily cover publications on this topic from the past 10 years, with a focus on the different formats of multi-pass transmembrane proteins. Finally, the remaining challenges facing this field and new technologies developed to overcome a number of obstacles are discussed.

Expression patterns of claudins in cancer

Claudins are four-transmembrane proteins, which were found in tight junctions. They maintain cell barriers and regulate cell differentiation and proliferation. They are involved in maintaining cellular polarity and normal functions. Different claudins show different expression patterns. The expression level and localization of claudins are altered in various cancers. They promote or inhibit proliferation, invasion, and migration of cancer cells through multiple signaling pathways. Therefore, claudins may serve as diagnostic markers, novel therapeutic targets, and prognostic risk factors. The important roles of claudins in cancer aroused our great interest. In the present review, we provide a summary of insights into expression patterns of claudins in cancer, which is more comprehensive and provides new ideas for further research.

Generation of Antibodies Selectively Recognizing Epitopes in a Formaldehyde-Fixed Cell-Surface Antigen Using Virus-like Particle Display and Hybridoma Technology

Efficient induction of target-specific antibodies can be elicited upon immunization with highly immunogenic virus-like particles (VLPs) decorated with desired membrane-anchored target antigens (Ags). However, for example, for diagnostic purposes, monoclonal antibodies (mAbs) are required to enable the histological examination of formaldehyde-fixed paraffin-embedded (FFPE) biopsy tissue samples. Aiming at the generation of FFPE-antigen-specific mAbs and as a proof of concept (POC), we first established a simplified protocol using only formaldehyde and 90 °C heat fixation (FF90) of cells expressing the target Ag nerve growth factor receptor (NGFR). The FF90 procedure was validated using flow cytometric analysis and two mAbs recognizing either the native and FFPE-Ag or exclusively the native Ag. C-terminally truncated NGFR (trNGFR)-displaying native and FF90-treated VLPs derived from HIV-1 did not reveal distinctive changes in particle morphology using transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis. Mice were subsequently repetitively immunized with trNGFR-decorated FF90-VLPs and hybridoma technology was used to establish mAb-producing cell clones. In multiple screening rounds, nine cell clones were identified producing mAbs distinctively recognizing epitopes in FF90- and FFPE-NGFR. This POC of a new methodology should foster the future generation of mAbs selectively targeting FFPE-fixed cell-surface Ags.

Tight Junction Protein Signaling and Cancer Biology

Tight junctions (TJs) are intercellular protein complexes that preserve tissue homeostasis and integrity through the control of paracellular permeability and cell polarity. Recent findings have revealed the functional role of TJ proteins outside TJs and beyond their classical cellular functions as selective gatekeepers. This is illustrated by the dysregulation in TJ protein expression levels in response to external and intracellular stimuli, notably during tumorigenesis. A large body of knowledge has uncovered the well-established functional role of TJ proteins in cancer pathogenesis. Mechanistically, TJ proteins act as bidirectional signaling hubs that connect the extracellular compartment to the intracellular compartment. By modulating key signaling pathways, TJ proteins are crucial players in the regulation of cell proliferation, migration, and differentiation, all of which being essential cancer hallmarks crucial for tumor growth and metastasis. TJ proteins also promote the acquisition of stem cell phenotypes in cancer cells. These findings highlight their contribution to carcinogenesis and therapeutic resistance. Moreover, recent preclinical and clinical studies have used TJ proteins as therapeutic targets or prognostic markers. This review summarizes the functional role of TJ proteins in cancer biology and their impact for novel strategies to prevent and treat cancer.

Dual display hemagglutinin 1 and 5 on the surface of enveloped virus-like particles in silkworm expression system

Rous sarcoma virus-like particles (RSV-LPs) displaying hemagglutinins of H1N1 (A/New Caledonia/20/99) (H1) and H5N1 (A/Vietnam/1194/2004) (H5) of the influenza A virus were produced. The H1 has its transmembrane domain, but the H5 was fused with the transmembrane domain of glycoprotein 64 (BmGP64) from Bombyx mori nucleopolyhedrovirus (BmNPV). H1 and RSV Gag protein were coexpressed in the hemolymph of silkworm larvae, copurified, and confirmed RSV-LP displaying H1 (VLP/H1). Similarly, the RSV-LP displaying H5 (VLP/H5) production was also achieved. Using fetuin agarose column chromatography, RSV Gag protein-coexpressed H1 and H5 in silkworms were copurified from the hemolymph. By immuno-TEM, H1 and H5 were observed on the surface of an RSV-LP, indicating the formation of bivalent RSV-LP displaying two HAs (VLP/BivHA) in the hemolymph of silkworm larvae. VLP/H1 induced the hemagglutination of red blood cells (RBCs) of chicken and rabbit but not sheep, while VLP/H5 induced the hemagglutination of RBCs of chicken and sheep but not rabbit. Additionally, VLP/BivHA allowed the hemagglutination of RBCs of all three animals. Silkworm larvae can produce RSV-LPs displaying two HAs and is a promising tool to produce the bivalent enveloped VLPs for the vaccine platform.

Protein nanoparticles directed cancer imaging and therapy

Cancer has been a serious threat to human health. Among drug delivery carriers, protein nanoparticles are unique because of their mild and environmentally friendly preparation methods. They also inherit desired characteristics from natural proteins, such as biocompatibility and biodegradability. Therefore, they have solved some problems inherent to inorganic nanocarriers such as poor biocompatibility. Also, the surface groups and cavity of protein nanoparticles allow for easy surface modification and drug loading. Besides, protein nanoparticles can be combined with inorganic nanoparticles or contrast agents to form multifunctional theranostic platforms. This review introduces representative protein nanoparticles applicable in cancer theranostics, including virus-like particles, albumin nanoparticles, silk protein nanoparticles, and ferritin nanoparticles. It also describes the common methods for preparing them. It then critically analyzes the use of a variety of protein nanoparticles in improved cancer imaging and therapy.

Nanotechnology-empowered vaccine delivery for enhancing CD8+ T cells-mediated cellular immunity

After centuries of development, using vaccination to stimulate immunity has become an effective method for prevention and treatment of a variety of diseases including infective diseases and cancers. However, the tailor-made efficient delivery system for specific antigens is still urgently needed due to the low immunogenicity and stability of antigens, especially for vaccines to induce CD8⁺ T cells-mediated cellular immunity. Unlike B cells-mediated humoral immunity, CD8⁺ T cells-mediated cellular immunity mainly aims at the intracellular antigens from microorganism in virus-infected cells or genetic mutations in tumor cells. Therefore, the vaccines for stimulating CD8⁺ T cells-mediated cellular immunity should deliver the antigens efficiently into the cytoplasm of antigen presenting cells (APCs) to form major histocompatibility complex I (MHCI)-antigen complex through cross-presentation, followed by activating CD8⁺ T cells for immune protection and clearance. Importantly, nanotechnology has been emerged as a powerful tool to facilitate these multiple processes specifically, allowing not only enhanced antigen immunogenicity and stability but also APCs-targeted delivery and elevated cross-presentation. This review summarizes the process of CD8⁺ T cells-mediated cellular immunity induced by vaccines and the technical advantages of nanotechnology implementation in general, then provides an overview of the whole spectrum of nanocarriers studied so far and the recent development of delivery nanotechnology in vaccines against infectious diseases and cancer. Finally, we look forward to the future development of nanotechnology for the next generation of vaccines to induce CD8⁺ T cells-mediated cellular immunity.

Claudin 6: Therapeutic prospects for tumours, and mechanisms of expression and regulation (Review)

Tight junctions (TJs) are an important component of cell connectivity; they maintain cell polarity, permeability and adhesion, and participate in the regulation of cell proliferation and differentiation. The claudin (CLDN) family is integral to TJs, and CLDN6 is an important member of this family. Abnormal expression of CLDN6 can destroy the integrity of TJs through various mechanisms and can serve multiple roles in the occurrence and development of tumours. CLDN6 is widely expressed in various tumours but rarely expressed in healthy adult tissues. The aim of this review is to critically examine the recent literature on CLDN6, including its structure, expression in different tumours, regulatory mechanisms and therapeutic prospects. Although some conclusions are controversial, in certain tumours, such as liver, ovarian, endometrial and oesophageal cancer, and atypical teratoid/rhabdoid tumours, research consistently shows that CLDN6 is expressed in tumour tissues but is not expressed or is expressed at low levels in surrounding tissues. In these tumours, CLDN6 has potential as a carcinoembryonic antigen and a therapeutic target.

Neospora caninum antigens displaying virus-like particles as a bivalent vaccine candidate against neosporosis

Neospora caninum is a causative and transmissible agent of dog and bovine neosporosis. The resulting reproductive failures in infected cattle lead to significant economic losses worldwide. However, there is no satisfactory treatment or vaccine currently available to combat this pathogen. Thus, the development of appropriate vaccines to manage its infection and transmission is urgently needed. In this study, we expressed Rous sarcoma virus-like particles (RSV-LP) that displayed dual N. caninum antigens in silkworms. The antigen candidates are modified by adding a transmembrane domain of GP64 protein from Bombyx mori nucleopolyhedrovirus (BmNPV) to the C-terminus of surface antigen 1 (NcSAG1) and SAG1-related sequence 2 (NcSRS2). The NcSRS2 alone or the NcSAG1/NcSRS2 bivalent form displaying RSV-LPs were purified using sucrose density gradient centrifugation. These purified VLPs were then used for immunizations in gerbils, Meriones unguiculatus, to evaluate the anti-N. caninum effects in vivo. The results demonstrated that antigens displaying RSV-LPs in immunized gerbils produced the antigen-specific antibody, leading to a relatively lower parasite load after infections of N. caninum. To the best of our knowledge, this is the first study to present an RSV-LP vaccine displaying bivalent antigens from neosporosis. Taken together, our strategy suggests that silkworm-expressed virus-like particles (VLPs) are promising bivalent vaccine candidates against N. caninum infections.

Nanovaccines for cancer immunotherapy

The past few decades have witnessed the booming field of cancer immunotherapy. Cancer therapeutic vaccines, either alone or in combination with other immunotherapies such as adoptive cell therapy or immune checkpoint blockade therapy, are an attractive class of cancer immunotherapeutics. However, cancer vaccines have thus far shown suboptimal efficacy in the clinic. Nanomedicines offer unique opportunities to improve the efficacy of these vaccines. A variety of nanoplatforms have been investigated to deliver molecular or cellular or subcellular vaccines to target lymphoid tissues and cells, thereby promoting the potency and durability of anti-tumor immunity while reducing adverse side effects. In this article, we reviewed the key parameters and features of nanovaccines for cancer immunotherapy; we highlighted recent advances in the development of cancer nanovaccines based on synthetic nanocarriers, biogenic nanocarriers, as well as semi-biogenic nanocarriers; and we summarized newly emerging types of nanovaccines, such as those based on stimulator of interferon genes agonists, cancer neoantigens, mRNA vaccines, as well as artificial antigen-presenting cells. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease.

Highly Efficient and Selective CAR-Gene Transfer Using CD4- and CD8-Targeted Lentiviral Vectors

Chimeric antigen receptor (CAR)-modified T cells have revealed promising results in the treatment of cancer, but they still need to overcome various hurdles, including a complicated manufacturing process. Receptor-targeted lentiviral vectors (LVs) delivering genes selectively to T cell subtypes may facilitate and improve CAR T cell generation, but so far they have resulted in lower gene delivery rates than conventional LVs (vesicular stomatitis virus [VSV]-LV). To overcome this limitation, we studied the effect of the transduction enhancer Vectofusin-1 on gene delivery to human T cells with CD4- and CD8-targeted LVs, respectively, encoding a second-generation CD19-CAR in conjunction with a truncated version of the low-affinity nerve growth factor receptor (ΔLNGFR) as reporter. Vectofusin-1 significantly enhanced the gene delivery of CD4- and CD8-LVs without a loss in target cell selectivity and killing capability of the generated CAR T cells. Notably, delivery rates mediated by VSV-LV were substantially reduced by Vectofusin-1. Interestingly, a transient off-target signal in samples treated with Vectofusin-1 was observed early after transduction. However, this effect was not caused by uptake and expression of the transgene in off-target cells, but rather it resulted from cell-bound LV particles having ΔLNGFR incorporated into their surface. The data demonstrate that gene transfer rates in the range of those mediated by VSV-LVs can be achieved with receptor-targeted LVs.

Rapid and Sensitive Detection of the Interaction of Human Papillomavirus Virus-Like Particles with Yeast Whole Cell RNA Using Biolayer Interferometry

RNA is a potential contaminant encountered in the production of recombinant yeast products such as proteins and virus-like particles (VLPs) and can be a particular concern when RNA associates with the product of interest. In this study a method to monitor and quantify the interaction of RNA with yeast-expressed human papillomavirus (HPV) VLPs using biolayer interferometry (BLI) is developed. Both biosensors with immobilized VLPs as well as biosensors with immobilized RNA are tested. Two types of recombinantly expressed HPV VLPs are used, Type 18 and Type 11. The data show that yeast whole cell RNA associates with Type 18 but not with Type 11 (maximum binding signal of 0.20 ± 0.02 nm on immobilized VLP probes for Type 18 vs. 0.03 ± 0.01 nm for Type 11). Additionally, the results show that a higher ionic strength weakens the affinity by both decreasing the association rate and increasing the dissociation rate, resulting in the dissociation constant increasing from 0.48 × 10^-9 to 2.1 × 10^-9 M, with phosphate ions having a greater effect on the reduction of association compared to chloride ions.